Honeywell ERM5220R1018 Install Manual page 15

Symptom
No outdoor
temperature shown on
thermostat
Thermostat shows "—"
for outdoor
temperature
Outdoor temperature
reading at thermostat
is too high
Compressor doesn't
turn on, "Y" LED is
blinking
Emergency backup
control doesn't function
(if configured as boiler)
Possible Cause
No wired outdoor
temperature sensor
connected to ERM, or
device configured as
boiler
Wired outdoor
temperature sensor
failed
Sun load on sensor
5-minute compressor
lockout after power
cycle
No valid indoor
temperature sensor
15
Action
Connect outdoor
temperature sensor to
S1/S1 terminals.
Device only reports
outdoor temperature
temperature when
configured as
compressor.
Check sensor for short
circuit or open circuit.
Verify outdoor
temperature sensor is
not in direct sunlight.
May need to use
longer wire to mount in
ideal location.
Wait 5 minutes,
compressor will turn
on after safety timeout.
Check sensor for short
circuit or open circuit,
or install indoor
temperature sensor on
S1/S1 terminals.
33-00135EFS—05